body {
    font-family: "Microsoft YaHei" , monospace;
    font-size: 16px;
}

.single-bg {
    background-image: url(/img/background_1.jpg);
    background-color: #fff;
    background-size: cover;
    width: 100vw;
    height: 100vh;
    position: fixed;
    top: 0;
    left: 0;
}

.single-bg:after {
    content: "";
    position: fixed;
    width: 100vw;
    height: 100vh;
    top: 0;
    left: 0;
    background: rgba(246,246,246,.9);
}

.loginBtn {
    width: 168px;
    height: 40px;
    font-size: 15px;
    outline: none;
    border-radius: 500px;
    border: 2px solid #a7a7a7;
    background-color: transparent;
    text-shadow: 1px 1px 8px rgba(0,0,0,.15);
}

.loginBtn:focus {
    box-shadow: 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}

.main {
    height:530px;
    width:1008px;
    padding:30px 0;
    top:50%;
    margin :-265px 0 0 -504px;
    position:absolute;
    left:50%;
    background-color: rgba(255,255,255,.9);
}